1. Field of the Invention
The invention relates to a distributing boom for stationary or mobile concrete pumps of the type mentioned herein.
2. Prior Art
Known distributing booms of this kind consist essentially of a rotary head rotatable about an axis of rotation in the form of a vertical axis, and of an arm assembly which is made up of a plurality of boom arms which can be telescoped or pivoted relative to one another. The arm assembly is attached articulated at one end of the first boom arm to the rotary head and, by means of a first cylinder/piston unit which has its ends articulated at points of articulation of the rotary head and of the first boom arm, can be pivoted about a horizontal axis of inflection between a substantially horizontally oriented retracted position and an operating position.
The distributing boom serves in a concrete pump as a support for a concrete supply line. Fluid concrete, which is introduced continuously into a material collecting container during concreting, is delivered via the concrete supply line to a concreting site which is arranged away from the stationary site of the vehicle. The arrangement of the boom arms of the arm assembly and the articulation points disposed between the same is matched with one another so that the distributing boom in its retracted position can be placed space-savingly on an associated substructure or chassis. By activating the drive assemblies between the boom arms the distributing boom can be brought into its operating position in which the boom tip can be guided by its end hose over the area which is to be concreted. Particular importance in respect of the retracting and extending process is placed on the deflection joint between the first boom arm and the rotary head and the cylinder/piston unit which is mounted there. If the arm assembly is located in the horizontally extended position then the greatest load moment is produced from the inherent weight of the arm, the operating load and the maximum distance of the center of gravity from the first axis of inflection. The relevant cylinder/piston unit must thus apply the highest force in this position to support the extended arm assembly. If the arm assembly is brought into the vertical position then with each increase in the setting angle the distance of the center of gravity of the arm assembly relative to the first axis of inflection is reduced. The same applies when the individual boom arms are moved towards the rotary head. This has the result that the cylinder force of the first cylinder/piston unit drops and from a certain distance of the center of gravity in relation to the cylinder engagement point a force level is reached from which a reduction of the cylinder diameter would basically be possible.